JP5829436B2 - Production method of transparent glass or transparent glass by special clarification method - Google Patents

Description

  The present invention relates to a method for producing transparent glass or transparent pulled glass by special process parameters and a special clarification method.

  The plate glass is glass that is produced in a flat shape regardless of the production method. Today, flat glass is manufactured mainly by two manufacturing methods, a float method and a roll-out method.

  Most flat glass is now manufactured by the float process. The float glass is usually transparent soda lime glass. In production, the raw material as a batch is melted at a temperature of 1500 ° C., and the glass melt is sent through a groove to a flat molten tin bath (float bath) in a protective gas atmosphere. The light glass melt floats or floats on the surface of the molten metal. In the molten state, like other melts, the metal property that the surface forms a smooth surface by surface tension is utilized. Tin has a melting point of 238 ° C., which is clearly lower than the softening point of the glass, and is almost three times the weight of glass. Accordingly, the glass floats on the molten tin and forms a glass surface whose both surfaces are completely parallel to each other. In the float process, molten glass floats on an ideal smooth surface of molten tin and solidifies with a surface quality that is not a problem as a ready-made glass, but a tin with a much lower melting point remains molten (Non-Patent Document 1 and Non-Patent Document 1). (See Patent Document 2).

  Cast glass is produced by rolling glass. It is produced by a non-continuous method called rolling by pouring into a plate, or a method called casting between rollers by continuously pouring from a tank. The rolling process results in a rougher glass surface and lower strength than float glass (see Non-Patent Document 3 and Non-Patent Document 4).

  Although not as important as the float method and the roll-out method, special glass such as window glass and modeling glass can be produced together with thin plate glass by a so-called pulling method as a third method for producing plate glass. Pulled glass is generally continuously produced by a pulling method using a mechanical device (see Non-Patent Document 5 and Non-Patent Document 6).

  Today, pulling glass is replaced by float glass and only a small amount is produced. This applies, for example, to the production of special glasses that are difficult or impossible to produce with the float process or that have to meet special requirements. For example, ultra-thin glass for liquid crystal displays, cover glass, that is, glass for covering the second glass layer, and the like are manufactured by a pulling method.

  In the production of pulling glass, batches of various raw materials and, in some cases, recycled glass and broken pieces of broken products are prepared. The batch is charged into a melting tank and a glass melt is produced at a temperature of 1470 ° C. or higher. The melting zone is followed by the fining zone, ie when the glass batch is melted, it is clarified. Clarification in glass production refers to the removal and elimination of bubbles in molten glass. Bubbles are defects in the glass that must be removed to eliminate external gases and bubbles to ensure a reasonable glass quality. Bubbles in the glass melt tend to rise to the surface. The rising speed of the bubbles depends on the diameter of the bubbles, and large bubbles rise faster than small bubbles. The basic principle at the time of clarification is the mixing of small bubbles due to large bubbles rising fast, that is, bringing additional bubbles into the glass and lifting the existing bubbles out of the glass to remove them. For example, Non-Patent Document 7 describes the behavior and removal of gas or bubbles in a glass melt.

  Viscous molten glass has a slow rate of ascent of small bubbles and requires a propulsion measure that can be carried out in an economical time. One example is physical or mechanical refining, in which gas bubbles such as water vapor, oxygen, nitrogen, and air are blown from the bottom opening of the melting furnace to reduce bubble components (bubbling).

  Unlike physical or mechanical fining, chemical fining decomposes or dissipates one or more compounds that produce a gas phase at a certain temperature range. By releasing the additional gas phase, the volume of existing bubbles is increased and buoyancy is increased, so that the desired clarification effect can be provided. In the industrial glass production by the glass tank, chemical clarification has been mainly important so far. Usually, a clarifier is added to the batch for clarification.

  Due to the high viscosity of the melt, fining is usually carried out gradually and usually requires a high temperature above or above the melting zone. Accordingly, the normal temperature during clarification is 1470 ° C. or higher, which is the same as the melting temperature range. Clarification is very important because glass quality is affected by clarification.

  Known fining agents in pulling glass production include redox fining agents such as antimony oxide or arsenic oxide. Other multivalent ions generated in at least two oxidation steps are also known. Furthermore, evaporative fining agents, that is, chlorides and fluorides such as sodium chloride, which are compounds that evaporate at high temperatures due to their vapor pressure, are known.

  The glass is then formed in the fining zone, which is carried out at a lower temperature than the melting and fining of the glass. Depending on the desired product, the glass can be formed by various forming methods. In this article, the pulling method is taken up as a forming method. After molding, in some cases, surface treatment and / or surface treatment of the glass can be continued.

  In the case of continuous production of pulled glass, for example on an industrial scale, the order of the described process steps is spatially divided rather than temporally, and the batch quantity supplied usually corresponds to the glass yield. .

  The use of antimony oxide as a fining agent has been shown to be detrimental. Antimony is a heavy metal. Because heavy metals are not metabolized in the body and cannot be decomposed, they are harmful and toxic to human tissues. Usually, heavy metals have an accumulating action, and even a trace amount accumulates in bones, teeth, brain, etc., and exhibits chronic toxicity that impairs the function of the nervous system. Similarly, immune defenses can be damaged.

  Environmental requirements have also increased, and the prohibition of the use of health harmful substances such as arsenic, antimony and lead on glass is required. Heavy metals can be toxic not only to the human body but also to environments such as animals and plants. Therefore, it is important to avoid heavy metals as much as possible to eliminate health risks and prevent environmental impact. Similarly, in the present invention, importance is attached to not using a clarifying agent harmful to health such as arsenic oxide. Another object of the present invention is to replace high cost fining agents such as cerium oxide with one or more other fining agents that can be produced at a clearly lower cost.

  In any case, the fining agent selected must meet the high requirements set for the fining agent because fining greatly affects the quality of the pulling glass produced. In other words, it must be ensured that there are as few bubbles as possible in the melt and in the drawn glass produced.

  From the prior art, the following method with a sulfate clarifier is disclosed.

Patent Document 1 describes an alkali-free glass and a method for producing the same, and 0.01 to 5% by weight of sulfate in terms of SO ₃ is added to the raw material as a refining agent.

  Patent document 2 is disclosing the manufacturing method of the glass melt which added the sulfate (except sodium sulfate) for clarification.

  Patent Document 3 relates to a degassing apparatus for a molten glass under reduced pressure, and mentions sulfate clarification in the paragraph [0020] of the specification.

Further Patent Document 4, a batch prepared adding at least clarifying agent, batch charging, glass melting, relates to a process for the preparation of borosilicate glass of hydrolytic class 1 according to process steps that thermoforming of the molten glass, converted to SO ₃ in the glass batch 0.01% to 0.8% by weight of sulfate is added.

  However, these prior art methods do not provide the desired high quality of glass because fining is not tailored to each glass and is practiced as a general method for all glasses as well.

European Patent Application Publication No. 1878709 (A1) Specification U.S. Pat. No. 1,488,915 European Patent Application Publication No. 1439148 (A2) Specification European Patent Application No. 1266682 (A1) Specification

Günther Noelle (Günter Nelle), Technik der Glasherstellung (Glass Manufacturing Technology), 3rd revised edition, Deutscher Verlag fuer Grundstoffindustrie (Germany), 44 -145 pages H. G. Pfaender (HG Pfender), SCHOTT Glaslexicon (SCHOTT glass lexicon), 5th edition, mvg-Verlag im Verlag industry, AG (mvg-Fairrk im Fairlar model L, model AG) (Landsberg am Lech), 1997, 56 pages or less Günther Noelle (Günter Nelle), Technik der Glasherstellung (Glass manufacturing technology), 3rd edition, Deutscher Verlag fuer Grundstoffindustrie (Dutcher Fairgart Hürtstudt, Gütner Gühlstuhl -144 Walter Koenig (Walter Konig) and Lambert v. Reis (Lambert v. Rice) and Rudolf Simon (Rudolf Zimon), Flachglas (sheet glass), Academische Verlagsgesellschaft M.M. B. H. (Academicche Fair Larks Gesellshaft M.B.H.), Leipzig, 1934, 43 pages or less Günther Noelle (Günter Nelle), Technik der Glasherstellung (Glass Manufacturing Technology), 3rd edition, Deutscher Verlag fuer Grundstoffindustrie (45), Deutscher Verlag Hürtstuhl -149 Walter Koenig (Walter Konig) and Lambert v. Reis (Lambert v. Rice) and Rudolf Simon (Rudolf Zimon), Flachglas (sheet glass), Academische Verlagsgesellschaft M.M. B. H. (Academicche Fair Larks Gesellshaft M.B.H.), Leipzig, 1934, 1 page or less H. Jebsen-Marwedel (H. Jepsen-Malwedel) and R.E. Brueckner (R. Bruckner), Glastechnische Fabricsfehrer (manufacturing defects in glass technology), 3rd edition, Springer-Verlag (Springer Fairlag), 195 pages or less

  Accordingly, an object of the present invention is to clarify the glass melt as efficiently as possible without using heavy metal clarifiers of antimony oxide and arsenic oxide in the method for producing transparent pulled glass, and to have no bubbles or few bubbles. It is to produce high quality glass. Use as little toxic fining agents as possible. Furthermore, the method of the present invention allows for the cheapest clarification of the glass melt.

The present invention solves the above problems by the following steps:
(A) Melting of raw materials while holding a glass batch melt,
(B) clarification of the produced glass batch melt,
(C) homogenization of the produced glass batch melt, and (d) production of glass products by the pulling method,
A method for producing transparent glass or transparent pulled glass, comprising:
Using a predetermined amount of sulfate clarifier selected from alkali sulfate, alkaline earth sulfate or zinc sulfate, or mixtures thereof as a clarifier;
In the clarification of the glass batch melt, it is about 0 ° C to 100 ° C, desirably about 30 ° C to 60 ° C, compared to the clarification method using a clarification system containing only antimony oxide or a combination of one or more other clarification agents. Adjust to the specified clarification temperature that is set high,
Sulfate clarifier amount, following steps:
(1) Measure the amount of released gas of the standard synthesis as a function of temperature by the standard measurement method where the fining agent contains antimony and sulfate, and determine the total amount of released gas from this,
(2) Add various sulfate amounts, measure the same process conditions as the standard synthesis, the same glass composition, the amount of released gas of synthesis by pure sulfate clarification by the same standard measurement method as a function of temperature, From this, determine the total amount of released gas,
(3)
- to create a curve based on step total quantity of released gas as a function of the sulfate amount used by _{(2) (SO 3) (} SO 2 + O 2),
Plotting the total amount of released gas determined as a function of the amount of sulfate (SO ₃ ) used as a reference in step (1),
By reading the amount of sulfate (SO ₃ ) to be used, which is required in the case of the total amount of outgas (SO ₂ + O ₂ ) similar to the reference,
Determining the amount of sulfate fining agent to be used based on the values determined from step (1) and step (2);
It is solved by providing a manufacturing method of determining according to the above.

  The method for producing transparent glass or transparent pulled glass according to the present invention comprises the steps of melting the raw material of the produced glass, clarification of the produced glass melt, homogenization, and possibly subsequent conditioning of the glass, and the desired glass product by the pulling method. Includes manufacturing process steps.

  First, glass raw materials are selected, and the raw materials are mixed to form a batch. The raw material ratio is determined by the type (batch) of the glass to be produced.

  Glass fragments can also be added to the batch to expedite melting. The glass fragment ratio can be, for example, 20% to 75%, depending on the desired glass quality and availability. Batch manufacturing can be by lot, continuous production, small scale or large scale production. For large-scale industrial production, batch manufacturing is fully automatic.

  The prepared batch is then fed to the melting apparatus. In a preferred form of the invention, the batch is melted in a melting tank, particularly preferably a continuous tank (Glaschmelzoefen (glass melting furnace), W. Trier (W. Trier), Springer Verlag (Springer Fairlag), Berlin Heidelberg New York Tokyo, 1984, see page 1). The continuous tank is processed without interruption, that is, the batch is charged and melted, and the molten glass is taken out. Energy is supplied to the melting tank by heating with an oil burner and / or a gas burner. Air (air fuel) or oxygen (oxygen fuel) can be used as the oxidant. The operation period of the melting tank can be several years.

  Next to the melting zone is the clarification zone. As is well known, clarified glass with sulfates usually does not meet the high quality requirements of special flat glass. General values for air bubbles in glass are float glass and rolled glass, which are on the order of 10 bubbles / kg or more (DIN EN glass (architecture) 572-1, 572-2, 572-4). The specifications / requirements for air bubbles in special plate glass are usually 5 bubbles / kg or less. Surprisingly, the present invention completely eliminates heavy metal fining agents such as antimony oxide, or other fining agents that are harmful to health such as arsenic oxide, alkaline sulfates, alkaline earth sulfates, zinc sulfates, mixtures thereof Even when replaced by a sulfate fining agent such as clarified, it has been shown that the specifications / requirements of special flat glass are met. Thus, the pure sulfate clarification according to the present invention produces a high quality pulled glass with no or few bubbles, with the advantage of eliminating any heavy metals. In other words, it is clear that it has good health and environmental benefits without heavy metals.

  In order to obtain the desired fining result in the glass melt, the sulfate fining agent according to the present invention is used to maintain the absence of bubbles as desired, to prevent foam formation, and to prevent temperature drop due to foam formation. Heating at the time of clarification is often required. In general, fining using antimony oxide as a fining agent requires a temperature of 1470 ° C., so that the present invention uses the same glass composition and the same process as the fining agent in the same process as the antimony oxide fining agent, particularly antimony oxide / sulfate. Heating at a clarification temperature of 0 ° C to 100 ° C, preferably 30 ° C to 60 ° C, is preferable to a normal clarification method using clarification. Therefore, in the pure sulfate clarification of this invention, the suitable temperature of 1480 to 1570 degreeC, desirably 1500 to 1530 degreeC is set.

  In the present invention, it is also possible to produce a glass composition that can be sufficiently clarified without increasing the clarification temperature. In that case, the heating of the clarification temperature is 0 ° C.

  In the production method according to the present invention, the energy supply during the clarification process is increased, that is, 0 ° C. to 100 ° C., preferably 30 ° C. to higher than the case of using a general clarification agent of antimony oxide or an antimony oxide / sulfate clarifier It is particularly preferable that the temperature during the clarification process is increased by about 60 ° C., while the energy supply of the melting zone, that is, the melting temperature itself is not particularly increased in the present invention. In the present invention, melting and clarification are carried out particularly in the same melting tank. Therefore, it is preferable to increase energy supply, that is, increase the temperature from the front of the melting tank where the batch melts to the rear of the melting tank where the clarification occurs. This can be achieved, for example, by appropriately adjusting and arranging the burner used in the melting tank. However, there are glass compositions that are suitable for setting a different energy supply.

  In clarification by the method of the present invention, in addition to energy supply, that is, introduction of energy into the melting tank, energy distribution in the melting tank is also important. It is particularly preferred that the melt tank is formed so that the energy distribution of the melt tank is advantageous for the fining process. Therefore, it is recommended that the shape of the melting tank be appropriately formed. For those skilled in the art, the judgment can be made with a slight judgment.

The sulfates that can be preferentially introduced in the invention are sodium sulfate, potassium sulfate, calcium sulfate, barium sulfate, or zinc sulfate. In sulfate refining, the sulfate refining agent used reacts with the usual SiO ₂ as follows to generate SO ₃ :
RSO ₄ + SiO ₂ → RO x SiO ₂ + SO ₃
R ₂ SO ₄ + SiO ₂ → R ₂ O x SiO ₂ + SO ₃
R. . . . . . . Alkaline earth metal R ₂ . . . . . . Alkali metal

SO ₃ further reacts to become the original clarification reagent of SO ₂ and 1 / 2O ₂ . The effect of the sulfate refining agent depends greatly on the solubility of SO ₃ or SO ₄ ^{2− in} the glass melt. Gas solubility in glass, gas bubble formation by fining agents, and glass melt viscosity are highly temperature dependent. The gas released in the form of bubbles by the fining agent can increase the small gas bubbles left in the melting process and raise it to be removed from the melt. However, it is necessary that sufficient clarification gas is dissolved in the glass so that the clarification temperature is released even at a high temperature.

When alkali sulfate, alkaline earth sulfate or zinc sulfate is used as a fining agent, sulfate is decomposed into oxide and SO ₃ as described above. For example, 100 wt% CaSO ₄ yields 41.19 wt% CaO and 58.81 wt% SO ₃ . Therefore, in the present invention, the addition amount of the sulfate clarifier in terms of SO ₃ is particularly in the range of 0.2 to 1.5% by weight, and more preferably in the range of 0.7 to 1.2% by weight.

In the present invention, the amount of sulfate fining agent is determined through the following steps:
(1) Measure the amount of outgassing of the reference synthesis as a function of temperature according to the standard measurement method where the fining agent contains antimony and sulfate, and determine the total amount of outgassing related to fining from this,
(2) Add various sulfate amounts, measure the same process conditions as the standard synthesis, the same glass composition, the amount of released gas of synthesis by pure sulfate clarification by the same standard measurement method as a function of temperature, From this, the total amount of released gas (SO ₂ + O ₂ ) is determined,
(3) Based on the values obtained from step (1) and step (2), the amount of sulfate clarifier to be used is determined.

The amount of gas “related to fining” refers to the amount of gas that contributes to fining, that is, SO ₂ + O ₂ in a certain temperature range.

The amount of sulfate clarifier used in step (3) is determined by:
- to create a curve based on step total quantity of released gas as a function of the sulfate amount used by _{(2) (SO 3) (} SO 2 + O 2),
Plotting the total amount of released gas determined as a function of the amount of sulfate (SO ₃ ) used as a reference in step (1),
-Read the amount of sulfate (SO ₃ ) to be used, which is necessary for the total amount of outgas (SO ₂ + O ₂ ) similar to the reference.

  The method according to the invention is described in detail below.

  (1) First, the amount of outgas for the reference synthesis is measured as a function of temperature. In the reference synthesis, the process conditions and glass composition are arbitrarily selected within a general range and the fining agent contains antimony and sulfate, so the method is consistent with the prior art. Based on this measurement.

  Based on the measured gas release amount, it is possible to calculate the total release gas amount in a temperature range (for example, 1250 to 1470 ° C. from the start of fining to the maximum reached glass temperature) related to the planned synthesis.

  (2) Next, the gas composition is measured using the same glass composition and the same process conditions as in the reference synthesis, but containing only sulfates and no antimony. Based on the gas emission measurement value, the total emission gas amount can be calculated in the same temperature range as the reference (from the start of clarification to the maximum glass temperature reached, for example, 1250 to 1470 ° C.). The total amount of released gas is determined for each amount of sulfate clarifier by changing the amount of sulfate clarifier to release all gas.

  In some cases, it may be appropriate to consider whether to use a sulfate or antimony-containing raw material for the production of glass. This can be useful, for example, when adding waste glass or debris. For example, unless the crushed pieces are brought to the maximum melting temperature or higher in the previous melting step, there is no clarification effect even if new sulfates are introduced, so the sulfate contained in the crushed pieces is not useful. However, since the clarification effect is 80 to 100%, it can be studied unconditionally, and thus reused antimony is important.

The measurement of gas release can be performed, for example, by batch gas profile measurement. Various batch components can be heated mainly at a heating rate of 6 K / min. For example, gas emissions up to a temperature of 1690 ° C. can be measured by mass spectrometry. Usually, a batch of 30 g is weighed with a quartz glass cuvette (φ80, height 50 mm). The cuvette is preferably subjected to an argon gas flow of 10 mL / min so that the discharge can be measured as soon as possible. Carbon dioxide (CO ₂ ), sulfur dioxide (SO ₂ ), and oxygen (O ₂ ) emissions can be quantitatively measured. Furthermore, qualitative analysis of nitrogen oxide (NO _x ) and water vapor was also conducted. The amount of gas evolution depending on the batch temperature was recorded. That is, the decomposition temperature range of nitrates, carbonates, and sulfates can be detected, as well as the liberation of absorbed and chemically bound water (as hydrates). A particularly noteworthy measurement is the SO ₂ and O ₂ emission ratio in the sulfate fining temperature range (> 1100 ° C.) (the amount of gas “related to fining”). Also, batch components of each content of sulfate (such as 0-2 wt% SO ₃ ) were tested with various alkali metal or alkaline earth metal compounds as sulfate carriers. For details, see for example F.A. W. Kraemer (FW Kramer), “Gaspromessengen zur Best munger der Gasabbebe beim Glasschmelzproess” (Glastechn. See Berichte 53 (1980), 177-188.

(3) Pure sulfate clarified sulfate based on the criteria to achieve the gas release achieved to the selected criteria by the correlation between a certain total released gas amount and the amount of sulfate clarifier used. The amount of fining agent used can be determined. To do so, first, as determined in step (2), a curve is created by plotting as a function of the sulfate amount (SO ₃ ) using the total released gas amount (SO ₂ + O ₂ ). In this drawing, the total emission gas amount calculated as a function of the reference sulfate amount (SO ₃ ) used in step (1) is plotted. In this way, the amount of sulfate (SO ₃ ) that exists and should be used in the case of the total amount of released gas (SO ₂ + O ₂ ) can be read as in the case of the reference.

  Related matters will be described again in detail when the drawings are described.

The method according to the invention is likewise considered particularly suitable when determining the maximum melting / fining temperature preferentially required for sulfate fining in the following steps:
(1 ') The amount of gas released from the reference synthesis according to the standard measurement method in which the fining agent contains antimony and sulfate is measured as a function of temperature, from which the temperature at which the maximum amount of gas related to fining is released is determined,
(2 ') Add various sulfate amounts, and measure the same process conditions as the reference synthesis, the same glass composition, and the amount of released gas of the synthesis by pure sulfate clarification by the same standard measurement method as a function of temperature. Determine the temperature at which the amount of outgassing is maximized,
(3 ′) The temperature difference of sulfate clarification (temperature heating) is determined based on the values obtained in (1 ′) and (2 ′).

In the present invention, preferentially, the temperature difference (temperature warming) of step (3 ′) is determined by:
- step as a function of the sulfate amount used (SO ₃₎ (2 _') by creating a curve from outgassing maximum outgassing measurements,
Read the maximum temperature of gas release based on the amount of sulfate (SO ₃ ) used in the fining agent and compare the read maximum temperature with a reference to determine the temperature difference to be introduced.

  Based on the gas release curve as a function of temperature, the temperature at which gas release is maximized can be determined. By plotting the maximum amount of gas released from the outgassing measurements as a function of the amount of sulfate added (the amount of clarifier) in batches of different sulfate amounts in pure sulfate clarified, the sulfate clarified relative to the reference The temperature heating in the case can be determined. Matters that are practically relevant will be described in detail again when the drawings are described.

  Another advantage of sulfate clarification according to the present invention is that the oxidation potential of the sulfate clarifier used relative to conventional antimony / sulfate clarification changes from the yellow tone in the case of clarification using antimony oxide, In the sulfate clarification according to the present invention, the color tone of the produced glass changes to blue tone. The blue-colored glass thus has a high degree of transparency and is brighter than the yellow tone using an antimony oxide clarifier. Since glass only touches the air in the liquid pulling method, both sides become “fire-making surfaces” and become transparent and increase shine. In the present invention, the highly transparent blue-colored pull-up glass produced according to the present invention is referred to by the term “transparent glass”. In the present invention, “highly transparent” means that the glass produced by the pulling method according to the present invention has a higher transmittance than the glass of the same component produced by the float process.

  The use of the sulfate clarifier according to the invention guarantees a particularly good quality for the absence of bubbles. By the method of the present invention, clarification can be carried out on the produced glass product, in which only 5 bubbles / kg or less, desirably 3 bubbles / kg or less, more desirably 1 bubble / kg or less is detected. This also includes microscopic bubbles that are visible.

  In the present invention, unexpectedly, the antimony oxide clarifier can be completely replaced by a sulfate clarifier, and when the desired clarification is carried out, it is practically optically blue with no inclusions or bubbles. High-transmission glass with high homogeneity and high spectral transmittance can be produced. In the production of solar glass by the roll-out method, for example, antimony is added as an oxidizing agent to make the glass have a white appearance. Therefore, it is not natural for those skilled in the art to consider pure sulfate clarification in the production of pulled glass / transparent glass.

  In addition to using sulfate clarifiers, the use of other clarifiers or reducing agents, particularly the addition of additives that change transmittance or color tone in addition to the original glass component, is not prioritized in the present invention. Therefore, in order to guarantee the maintenance of high transmittance, abandoning chemical decoloring agents such as Ni, Se and / or Co, without using halogen-containing fining additives such as chlorine or fluorine-containing fining agents, It is appropriate to completely eliminate carbon that may change the color tone by reduction, and to completely eliminate oxidizers that change the transmittance, such as cerium oxide. When divalent iron is generated, iron may be oxidized by the use of a fining agent and the color tone may change in an undesired range, so it is particularly preferred to minimize the iron content in the raw materials and manufacturing process. It is desirable that the glass produced in accordance with the present invention does not contain added iron, but only contains iron in an impurity form that is difficult to avoid. The acceptable iron content in the product is 40 to 200 ppm, desirably 50 to 150 ppm.

Additives to the glass composition are limited to compounds that do not adversely affect the properties of the glass being produced. For example, there is TiO ₂ that adjusts the UV edge.

  In the process of the invention, the fining zone is followed by homogenization and conditioning of the glass melt produced. This is done, for example, using a stirrer.

  In the next pulling method, the glass is formed into a desired shape. In the pulling method of the present invention, a well-known pulling method is used by those skilled in the art. The pulling methods employed in particular are the so-called downdraw method and updraw method. By the downdraw method (“upward pulling”) or the updraw method (“upward pulling”), the glass melt is pulled up or down from the draw tank by a slot die having a slit as a forming element. The glass width to be pulled is determined by the width of the pulling tank. The pulling speed used in the downdraw method or the updraw method is mainly in the range of 0.1 to 15 m / min, but may be higher or lower individually.

  In the pulling method of the present invention, the downdraw method is employed in the same manner as the overflow fusion method, the redraw method, and the nozzle method. Preferential updraw methods are the full call method, Asahi method, Libby Owens method, Colburn method, and Pittsburgh method. The use of the updraw method is particularly desirable in the present invention.

  A particularly desirable updraw method in the present invention is the full call method. Belgian engineer Emile Fullcor developed in 1905 the first flat plate pulling method, the so-called full call method. When the glass is pulled directly from the melt, it has been a problem that the formed glass plate shrinks due to surface tension and becomes thin glass fibers. The full coal method prevented this by pressing the heat-resistant material against the glass melt by means of a so-called slot die with an intermediate slit and a tapered top. The glass flows out of the slot die due to the hydrostatic pressure and is pulled up by a trap provided between the rollers. A so-called “onion” useful for forming a glass sheet with an even plastic melt is formed directly from the slot die. This onion is uniformly cooled by a so-called cooling cylinder. Both ends of the glass flowing out of the slot die, so-called edges, are somewhat thick and solidify faster than the middle part, so that glass shrinkage is prevented. The glass plate is pulled up by a puller having a number of roller pairs and cooled gradually. It moves vertically upward in a pulling / cooling tower with a height of about 6-10m. Since the cooling time depends on the pulling speed, the thin glass is shorter than the thick glass. A cutting table is provided in the upper part of the pulling tower, and the rising glass plate is cut and divided.

  A characteristic associated with pulled glass is that the slot die leaves an almost invisible thin streak that indicates the pulling direction of the glass. The glass thickness is set by expanding the slot die slit and changing the pulling speed. That is, a thick glass can be manufactured if the pulling is slow, and a thin glass can be manufactured if the pulling is fast. The pulling speed is limited by the glass viscosity of the onion, and a higher pulling speed can be selected as the viscosity increases.

  In the present invention, in addition to the full call method, the Asahi method finished as a variant of the full call method in which the slot die block and the pulling tower are changed is prioritized. The Asahi type slot die block is mainly composed of two rollers or beams arranged adjacent to each other in parallel, and is basically constructed and arranged so as to form a slit having the same function as the full call slot die.

  Other up-draw methods that can be used are the Libby Owens method or the Colburn method, which is a pulling method that produces plate glass without slot dies, unlike the full call method, and the upper 70 cm of the glass surface of the pulled glass plate changes from vertical to horizontal. Is done. In the present invention, the Pittsburgh method can be adopted finally. This is also a vertical pulling method for producing plate glass, which is a method of pulling the glass plate from the free melting surface unlike the full coal method.

  However, the full call method is particularly prioritized in the present invention.

  The glass that can be produced by the method of the present invention is not particularly limited. Thus, any transparent glass / pulled glass can be produced.

Since the solubility of SO ₃ or SO _{2 in} the glass melt depends on the basicity of the glass used, the use of a glass having a relatively high basicity in the present invention is particularly suitable for the action of the clarification method. . For example, a glass having a high content of alkali and / or alkaline earth is included. Since glass with a high alkali content and / or alkaline earth content is basic, the solubility of SO ₂ is high. The higher the basicity of the glass (alkali-containing and alkaline earth-containing), the greater the action of SO ₃ as a fining agent, based on SO ₂ solubility. Therefore, in the present invention, priority is given to the selection of glass based on so-called alkaline earth silicate glass. Zinc-containing glasses are particularly suitable because the zinc in the glass composition evaporates significantly under reducing conditions in the float bath and causes undesired reactions with the tin in the tin float bath, thus limiting the production in the float process.

In the present invention, priority is given to the production of alkaline earth silicate glass. This includes SiO ₂ , alkali oxides, and alkaline earth oxides as main components, and in some cases, other components are added.

The base glass usually contains at least 55% by weight, desirably at least 65% by weight of SiO ₂ . The maximum content of SiO ₂ is 75% by weight. Suitable content range of SiO ₂ is at 65 to 75 wt%, preferably to 69-72 wt%.

Of the alkali oxides, sodium and potassium are particularly important. The Na ₂ O content according to the present invention ranges from 0 to 15% by weight, preferably from 6 to 13% by weight, more preferably from 8 to 12.5% by weight. The glass composition produced in the present invention may not contain Na ₂ O at all (Na ₂ O = 0% by weight). In the present invention, the content of K ₂ O is 2 to 14% by weight, desirably 4 to 9% by weight.

The glass composition according to the invention, typically, Li ₂ O is not contained _(Li 2 O = 0% by weight). Since Li ₂ O is expensive as a raw material, it is desirable not to use it.

  If the alkali oxide is more or less than the predetermined content, the thermal expansion characteristic cannot be maintained.

  In particular, calcium, magnesium, and barium are used as alkaline earth oxides.

  CaO is used in the range of 3 to 12% by weight, desirably 4 to 9% by weight, more desirably 4.9 to 8% by weight.

  According to the present invention, MgO is used in the range of 0 to 4% by weight, desirably 0 to 3.6% by weight, more desirably 0 to 3% by weight. MgO can be used to improve crystal stability and raise the transformation temperature Tg. The glass composition of the present invention may not use MgO at all (MgO = 0% by weight).

  BaO is 0 to 15% by weight, desirably 0 to 8% by weight, more desirably 0 to 3% by weight, still more desirably 0 to 2.5% by weight, and particularly desirably 1.8 to 2.2% by weight. Use with a range. BaO can be used to increase the transformation temperature Tg of the glass composition. The glass composition produced according to the present invention may not use BaO at all (BaO = 0% by weight). The advantages of low BaO content are low density and low weight of the manufactured glass and cost reduction of expensive BaO components.

It is an advantage of the present invention that the glass composition produced according to the present invention does not contain B ₂ O ₃ . This is a desirable advantage because B ₂ O ₃ is highly toxic and the raw material is teratogenic as is well known, while it is an expensive component that clearly increases the glass manufacturing costs.

The Al ₂ O ₃ content is 0 to 15% by weight, desirably 0 to 8% by weight, and more desirably 0 to 2% by weight. This content may vary depending on the purpose of use. When the Al ₂ O ₃ content is 15% by weight or more, there is a disadvantage that the material cost increases and the meltability deteriorates. However, the Al ₂ O ₃ content may be 0% by weight.

  In the present invention, the ZnO content is 0 to 5% by weight, preferably 0 to 4.5% by weight. In particular, ZnO-containing glass cannot be practically produced by the float process due to the problem that zinc and tin react, but can be produced by the pulling method according to the present invention. Thus, the glass produced according to the invention particularly preferably contains at least 0.1% by weight of zinc oxide. In another preferred embodiment, the zinc oxide in the glass according to the invention has a content of more than 2.0% by weight.

Further, the glass composition according to the present invention may contain TiO _{2 in an amount} of 0 to 2% by weight, desirably 0 to 1.5% by weight. TiO ₂ can generally be used for UV blocking of glass.

In the manufactured glass, the Zr-containing tank material may corrode and Zr may be detected. In other cases, Zr is not positively added to the raw material (ZrO ₂ = 0% by weight) and is contained at most as a normal impurity.

The glass composition according to the present invention comprises As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , a halogen-containing fining agent, a chemical decoloring agent such as Ni, Se and / or Co, carbon, an oxidizing agent which changes the transmittance ( For example, it does not contain cerium oxide) and does not contain other reducing agents. It is also preferred to minimize the iron content and prevent undesirable discoloration of the glass being produced. Therefore, it is advantageous to take measures to minimize iron contamination in raw materials and processes without adding iron. It is particularly preferred to take measures to minimize contamination in the raw materials and processes according to the invention.

  Alkali sulfates, alkaline earth sulfates and / or zinc sulfate are used as fining agents. Special preference is given to sodium sulfate, potassium sulfate, barium sulfate, calcium sulfate or zinc sulfate.

Particularly suitable glass compositions that can be produced by the process of the invention comprise or consist of the following glass components (wt% oxide):
SiO ₂ 55~75 weight%
Na ₂ O 0-15% by weight
K ₂ O 2~14 weight%
Al ₂ O ₃ 0-15% by weight
MgO 0-4% by weight
CaO (total) 3-12% by weight
BaO 0-15% by weight
ZnO 0-5% by weight
TiO ₂ 0 to 2% by weight
CaO (CaSO ₄ ) 0.5 to 1.5% by weight

Another preferred glass composition of the present invention comprises or consists of the following components (weight percent of oxide).
SiO ₂ 65-75% by weight
Na ₂ O 8 to 13 wt%
K ₂ O 4~9 weight%
Al ₂ O ₃ 0 to 2% by weight
MgO 0-4% by weight
CaO (total) 4-9% by weight
BaO 0 to 3 wt%
ZnO 0-5% by weight
TiO ₂ 0 to 2% by weight
CaO (CaSO ₄ ) 0.5 to 1.5% by weight

Yet another preferred glass composition of the present invention comprises or consists of the following components (wt% oxide).
SiO ₂ 65-75% by weight
Na ₂ O 8-10% by weight
K ₂ O 6~9 weight%
CaO (total) 4-9% by weight
BaO 1-3 wt%
ZnO 3-5% by weight
TiO ₂ 0 to 2% by weight
CaO (CaSO ₄ ) 0.5 to 1.5% by weight

  The benefits obtained by the method of the present invention are quite diverse.

The method of the present invention avoids heavy metal clarifiers such as antimony oxide, clarifiers that are harmful to health such as arsenic oxide, or particularly expensive clarifiers such as CeO ₂ , and are not harmful to health and are inexpensive sulfate clarifiers. Can be replaced. Therefore, the pure sulfate clarification according to the present invention has the advantage of producing a high-quality pull-up glass without bubbles or with few bubbles at the same time without using any kind of heavy metals.

  Since the toxicity of sulfate fining agents is hardly significant, there is no practical limitation on the intended use of the production glass. The product clarified according to the present invention does not affect the environment because it uses a non-toxic clarifier. The sulfate clarification according to the present invention is a conventional clarification using a clarification temperature in particular ranging from 1480 ° C. to 1570 ° C., preferably from 1500 ° C. to 1530 ° C., preferably an antimony oxide containing clarifier or an antimony oxide / sulfate clarifier. The clarification temperature is 30 to 60 ° C. higher than the method. The production method of the present invention is preferable because the energy supply can be increased during the refining method. In order to promote the fining effect, the energy distribution of the melting tank can be changed. For example, the shape of the melting tank can be appropriately configured.

  Addition of a specified amount of sulfate according to the method described for measuring outgassing by changing the amount of sulfate fining agent compared to the standard, results in a very efficient fining, and the production glass is foamed and foamed. Excellent glass quality without any. For glass melts, the fining of the present invention establishes very efficient degassing / bubble removal. As the produced glass product, a product having 5 bubbles / kg or less, desirably 3 bubbles / kg or less, more desirably 1 bubble / kg or less is produced.

  Another advantage of the sulfate clarification of the present invention is that, instead of the clarified yellow tone glass using antimony oxide, a highly transparent, optically homogeneous and blue spectrally transparent glass is produced. And it is that it is shining from yellowish glass by blue tone. This is because a transparent glass having a higher transmittance than an equivalent float glass is produced by the method of the present invention.

The addition amount of the sulfate clarifier is mainly in the range of 0.2 to 1.5% by weight, preferably 0.7 to 1.2% by weight in terms of SO ₃ .

  In particular, the present invention does not prioritize the use of additives that change the transmittance and color tone separately from the original glass components such as other fining agents and reducing agents.

  The pulling method introduced in the present invention is not particularly limited within the scope of the present invention, and those skilled in the art can introduce a known pulling method. In particular, a so-called down draw method and an up draw method, preferably a so-called up draw method, more preferably a full call method are introduced.

  The method of the present invention presents an efficient and inexpensive clarification method, in particular for basic glasses as well as alkaline earth silicate glasses.

  It is anticipated by those skilled in the art that the method for producing transparent glass according to the present invention using the pulling method gives surprisingly good results by sulfate clarification without adding a reducing agent, unlike the production of soda-lime glass. Was not. This can be achieved by determining the process parameters described, heating the fining temperature, adjusting the amount of sulfate fining agent, or adapting the melt bath shape to maintain the best possible energy distribution in the bath. It can be achieved by the invention.

  The present invention is not limited to the described embodiments. If it is those skilled in the art, within the scope of the method of the present invention, for example, the type of sulfate clarifier used, the energy distribution of the melting tank, the shape of the melting tank, the type of glass to be produced, the structure and adjustment of the burner, batch charging A series of parameters such as technology structure and operation can be changed. Other changes and modifications are apparent to those skilled in the art from the prior art.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited thereto.

1 schematically illustrates an example embodiment of a method according to the invention. 3 shows three examples of glasses characterized based on the Lab color system. Shown are three curves obtained from a reference synthesis CO ₂ , SO ₂ , O ₂ outgassing measurement with an antimony / sulfate containing fining agent, showing the gas flow as a function of temperature. Shows curves obtained from outgassing measurements of synthetic CO ₂ , SO ₂ , O ₂ with varying amounts of clarifier containing sulfate without antimony, and displays gas flow as a function of temperature doing. Shows curves obtained from outgassing measurements of synthetic CO ₂ , SO ₂ , O ₂ with varying amounts of clarifier containing sulfate without antimony, and displays gas flow as a function of temperature doing. Shows curves obtained from outgassing measurements of synthetic CO ₂ , SO ₂ , O ₂ with varying amounts of clarifier containing sulfate without containing antimony, showing gas flow as a function of temperature doing. Shows curves obtained from outgassing measurements of synthetic CO ₂ , SO ₂ , O ₂ with varying amounts of clarifier containing sulfate without antimony, and displays gas flow as a function of temperature doing. Obtained from outgassing measurements of total outgassing flow (SO ₂ + O ₂ ) as a function of the amount of sulfate used (SO ₃ ) for Examples 5 and 6 with varying sulfate fining content. The two curves, the values obtained by the reference synthesis, and the curves assumed by the theory are shown. FIG. 8 shows the maximum outgassing (SO ₂ ) temperature determined from the outgassing curves of FIGS. 4-7 as a function of the amount of sulfate fining agent (weight% in terms of SO ₃ ).

  FIG. 1 schematically shows an exemplary embodiment of a method for producing transparent glass according to the invention. First a batch is produced, charged into a melting tank and melted there. This is illustrated in the continuous tank 100 shown schematically. It melts at a temperature in the range of 1470 ° C. by various burners (not shown) such as a gas burner. The batch melt in the form of molten glass 15 moves from the melting zone 10 to the clarification zone 20 where it is clarified. The fining agent of the present invention is a sulfate fining agent, and the temperature is 1480 to 1570 ° C, preferably 1500 to 1530 ° C. Thereafter, the molten glass 15 is homogenized in the zone 30.

  In the illustrated mechanism unit 40 of the continuous tank 100, for example, the full-coal method is shown as a method for pulling up the transparent glass manufactured by the invention. A slot die 50 made of, for example, Chamotte, which is pressed into the molten glass 15 and fixed, is provided. Glass is extruded from the slit of the slot die 50. A trap (not shown) is guided by glass pushed out from above, and the glass adheres to the trap and is pulled up vertically upward by a pulling tower 60 having a height of 6 to 8 m illustrated together with the glass plate. A glass plate 45 having a corresponding width is manufactured. The cooler 55 near the glass surface cools the glass temperature so that the glass dimensions are stable. The roller pairs 71 and 72 arranged in the pulling tower 60 guide the glass plate 45 and cool it at the same time.

  A so-called cutting table 80 for appropriately cutting the glass sheet is provided at the end of the pulling tower 60.

  FIG. 2 is described in detail in the following example.

  The amount of the sulfate refining agent and the temperature heating required at the time of refining can be suitably calculated in the present invention with reference to the following FIGS.

Determination of the preferred amount of sulfate fining agent for the method of the invention:
(1) First measure the amount of gas released (SO ₂ , O ₂ , CO ₂ gas flow) for reference synthesis and plot the value as a function of temperature. For the reference synthesis, process conditions and glass compositions are appropriately selected, the fining agent contains antimony and sulfate, and the method is carried out according to the prior art. From measurements of the gas emissions, associated temperature range for the reference synthesis (from clarified start up reaches the glass temperature, 1300 etc. ~1470 ℃) can be calculated on the total amount of gas released at.

In the example shown in FIG. 3, the curves of SO ₂ , CO ₂ , O ₂ contained in the measurement of the amount of gas released in a reference synthesis using one clarifier (gas flow as a function of temperature). The fining agent is a component of 0.5 wt% Sb ₂ O ₃ and 0.35 wt% CaO as CaSO ₄ (corresponding to 0.50 wt% SO ₃ ). Therefore, FIG. 3 is a reference curve.

(2) The amount of sulfate clarifier (antimony-free clarifier containing only sulfate as a component effective for clarification) is changed by the same process conditions and the same glass composition as in the standard synthesis of FIG. Measure the amount. Here too, from the measurement of the amount of gas released, the total amount of gas released in the same temperature range as the standard (from the start of clarification to the maximum reached glass temperature, such as 1300 to 1470 ° C.) can be calculated.

4 to 7 illustrate three curves of CO ₂ , SO ₂ , and O ₂ representing gas flow (gas release amount) as a function of temperature. Antimony free fining agents with varying sulfate content were used.

In FIG. 4, a fining agent composed of 0.325 wt% CaO (corresponding to 0.46 wt% in terms of SO ₃ ) is used as CaSO ₄ .

In FIG. 5, a fining agent composed of 0.49 wt% CaO (corresponding to 0.70 wt% in terms of SO ₃ ) is used as CaSO ₄ .

In FIG. 6, a fining agent composed of 0.63% by weight of CaO (corresponding to 0.90% by weight in terms of SO ₃ ) is used as CaSO ₄ .

In FIG. 7, a fining agent composed of 0.71 wt% CaO (corresponding to 1.02 wt% in terms of SO ₃ ) is used as CaSO ₄ .

Therefore, it is clear from FIGS. 4 to 7 that the amount of released gas (SO ₂ + O ₂ ) increases as the amount of sulfate clarifier increases. It should be mentioned in this relationship, but in order to display all sulfates in a unified manner, the sulfate in the sulfate clarifier is displayed in terms of SO _3. SO ₂ + O ₂ .

  Unless anti-mony, etc., the melting temperature is higher than the temperature at which the debris reaches the maximum in the melting process, sulfate does not have a refining effect on debris, so the ratio of debris to be used later is also considered in batch charging. This is an advantage.

  (3) Comparing the total gas emission of the pure sulfate clarification method with the total gas emission of the standard synthesis (antimony / sulfate clarifier) according to FIG. 3, the same emission gas in the same temperature range as in the standard synthesis A particularly suitable amount of sulfate fining agent can be determined for the amount.

  What is important in this connection is that any glass composition results in another curve of outgassing measurements. There is no following from one glass composition to another. In any glass composition, follow the procedure from step (1) to (3) as described above, that is, first select the reference composition, measure the gas release, and calculate the total amount of gas released. Thereafter, in order to calculate the total amount of gas released in the sulfate clarification, the pure sulfate clarification for the glass composition is measured. Both tests (reference and sulfate clarification) are compared to determine the amount of sulfate clarifier used which is particularly suitable in the present invention.

FIG. 8 compares the reference synthesis and pure sulfate clarification, with the total gas released (SO ₂ + O ₂ gas flow) as a function of the batch sulfate addition (sulfate clarifier). . In this example, the reference synthesis contains a fining agent consisting of 0.5 wt% Sb ₂ O ₃ and 0.5 wt% SO ₃ .

The straight line shown in FIG. 8 (“Linear”) represents a theoretical linear approach and is clearly different from the actual measured curve (“Exponential” curve). Therefore, the measured values and the combined curves of Example 5 (diamonds) and Example 6 (triangles) are shown. With respect to the reference, it can be seen from FIG. 8 that for a gas flow of 1000 mL / dT / 100 g that can be read from the y-axis, an amount of 0.5 wt% SO ₃ must be used (read from the reference x-axis). This is also shown in FIG. When adjusting the gas flow similar to the reference with respect to Example 5, when the reference height is moved to the right in FIG. 8 parallel to the x-axis and intersecting the curve of Example 5, 0.8 wt% The amount of SO ₃ can be read. This is also shown in FIG. Accordingly, in Example 6, the ratio is 0.93% by weight. In this way, the amount of sulfate used in the form of sulfate clarifying agent can be easily calculated. In Example 6, since the crushed pieces were added to the raw material, the amount of sulfate suitably used for achieving the desired clarification was set to 1% by weight based on the ratio of the crushed pieces.

  Comparing the synthesis with standard synthesis (antimony / sulfate clarification) and pure sulfate clarification, the amount of sulfate clarifier particularly suitable in the present invention can be determined directly and particularly good results are obtained.

Determination of a suitable temperature for sulfate clarification according to the invention:
As shown in FIGS. 4 to 7, as the amount of the sulfate clarifier increases, the amount of released gas also increases, and the temperature at which the maximum amount of SO ₂ is released shifts to a high temperature (that is, to the right side on the x axis). That is, the maximum release amount of SO ₂ is 1350 ° C. in FIG. 4, but is 1390 ° C. in FIG. 5, 1410 ° C. in FIG. 6, and 1420 ° C. in FIG.

If the gas release curve as a function of temperature is evaluated (in the examples of FIGS. 4-7), the temperature at which the maximum gas release is achieved can be determined. Plotting the maximum gas release from gas release measurements as a function of the amount of sulfate added in the batch (amount of sulfate fining agent) can lead to the desired warming of the temperature during fining. In other words, the maximum difference between the reference and the pure sulfate clarification by the selected sulfate amount presents the desired temperature warming data for the maximum temperature in the melting tank. FIG. 9 illustrates this. FIG. 9 shows the maximum temperature of maximum SO ₂ release as a function of SO ₃ addition (wt%) determined from FIGS. The reference maximum outgassing temperature was determined to be 1395 ° C. (see also FIG. 3). In the case of 1 wt% SO _{3 in} a batch, the maximum release is 1420 ° C. according to FIG. Therefore, a desirable standard temperature difference (delta) for heating the maximum temperature of the melting tank is 25 ° C. with respect to the standard.

  By comparing standard synthesis with pure sulfate clarification, a particularly desirable temperature for pure sulfate clarification according to the present invention can be determined.

  What is described in FIGS. 1 to 9 is only an example of a possible form of the method according to the invention. Accordingly, it should not be limited, but merely an example of a possible embodiment.

  In the following, the present invention will be described by way of examples described in accordance with the teachings of the present invention, but the present invention is not limited thereto.

(Glass composition)
A glass composition was selected and glass was produced according to the method of the present invention. The method of the present invention includes the steps of melting, clarification, homogenization, and introduction of the full coal method. Clarification was carried out in the temperature range of 1500-1530 ° C. As a fining agent, CaSO ₄ or a combination of Sb and CaSO ₄ was employed. Table 1 below summarizes the component values (analytical values) of the selected glass compositions. The difference in the total value is due to the measurement accuracy of the analytical measurement method.

(Adjustment of melting tank)
Examples 1 and 5 will be described below as adjustment of a desirable melting tank of the present invention.

a) Adjustment of melting tank in Example 1 The melting tank used has the following specifications.
3-port natural gas regeneration tank with electric melting support:
l × b × h = 7.5 m × 3.3 m × 0.5 m
Where
l. . . Length b. . . Width h. . . The height charge was 1-2 t / m ³ · day or 0.5 to 1 t / m ² · day.

General melt tank preparation (prior art) is as follows:
Melting temperature: 1460-1480 ° C
Melting tank energy distribution: 18-22 / 36/22 / 20-24%
Bubbling gas amount: 20-25 l / h
Bubbling gas: oxygen Table 2 below lists examples of adjustment of the melting tank when a glass composition according to Example 1 of Table 1 is produced according to the present invention. Adjustments listed as standards are the same as in the prior art. The preferred adjustment according to the present invention increased the melting temperature for pure sulfate clarification and appropriately modified the energy distribution of the melting tank.

b) Adjustment of melting tank in Example 5 The melting tank used had the following specifications.
4-port natural gas regeneration tank l × b × h = 10 m × 3.5 m × 1 m
Charge: 0.5 to 1 t / m ³ · day or 0.5 to 1 t / m ² · day

  In the following Table 3, the adjustment example of the melting tank at the time of manufacturing the glass composition according to Example 5 of Table 1 by this invention is hung up. Adjustments listed as standards are the same as in the prior art. The preferred adjustment according to the present invention takes into account that the melting temperature has been increased and the energy distribution of the melting tank has been appropriately modified.

  By adjusting the suitable melting tank according to the present invention, it is possible to produce a transparent glass particularly excellent in fining results.

(L-a-b color system)
In order to characterize the transparent glass produced according to the present invention by the Lab color system, the glasses of Examples 3, 5, and 7 were selected and characterized. The L-a-b color system is a color system developed so that a color tone can be grasped by a scale and a color can be defined regardless of the type of production or reproduction technology. The recognized color is defined by chromaticity coordinates of {L, a, b} coordinates in the color space. In Table 4 below, the measured values with the standard light source D65 are listed with a sample length of 20 mm for the selected example.

  In FIG. 2, the measured values obtained from Examples 3, 5, and 7 are displayed. All the glass samples tested had a length of 20 mm and were measured with a standard light source D65. The comparative glass (Example 3) with antimony / sulfate mixed fining shows a clear yellow-green color. When replaced with pure sulfate clarification, the color tone changed, and the same component and the same iron content resulted in a blue tone (Example 7). When the iron content of the glass was low (Example 5), the color tone changed slightly to a red-blue tone.

(Chromaticity coordinate comparison)
As already described for the L-a-b color system, the chromaticity coordinates of the color space are accurately represented by three coordinates. The following numerical values were measured by comparing the chromaticity coordinates of the transparent glass and float glass produced according to the present invention.

  The transparent glass according to the present invention had a transmittance L as high as 1%, and was clearly weaker in green tone than the standard float glass. Accordingly, the standard float glass is inferior in transparency to the bright transparent glass having excellent brightness according to the present invention.

  The glass composition produced according to the present invention did not use any commonly used antimony oxide fining agent, but exhibited excellent quality. The produced transparent glass had a slightly blue tone, high transparency, and a bright appearance. This transparent pull-up glass has 5 bubbles / kg or less, desirably 3 bubbles / kg or less, more desirably 1 bubble / kg (manufactured glass), which has practically few bubbles, high spectral transmittance, and optical properties. The homogeneity was high.

  Therefore, according to the present invention, a method for producing transparent glass or transparent pulled glass is provided for the first time without using a heavy metal fining agent, in particular, an antimony oxide fining agent, and the produced transparent glass has a desired high quality. Yes.

DESCRIPTION OF SYMBOLS 10 Melting zone 15 Molten glass 20 Clarification zone 30 Homogenization zone 40 Mechanism part 45 Glass plate 50 Slot die 55 Cooler 60 Pulling tower 71, 72 Roller pair 80 Cutting stand 100 Continuous tank

Claims (13)

The following steps:
(A) Melting of raw materials while holding a glass batch melt,
(B) clarification of the glass batch melt produced;
(C) homogenization of the glass batch melt produced, and (d) production of glass products by a pulling method,
A method for producing transparent glass or transparent pulled glass, comprising:
Using a predetermined amount of sulfate clarifier selected from alkali sulfate, alkaline earth sulfate or zinc sulfate, or mixtures thereof as a clarifier;
Wherein a fining the glass batch melts, only antimony oxide, or other one or more fining agents 0 ° C. to 100 ° C. rather higher setting than refining method using a fining system containing a combination of to have predetermined fining Adjust to temperature,
The amount of the sulfate fining agent is determined by the following steps:
(1) Measure the amount of released gas of the reference synthesis according to the standard measurement method in which the clarifier contains antimony and sulfate as a function of temperature, and determine the total amount of released gas (SO ₂ + O ₂ ) related to clarification from this,
(2) Add various sulfate amounts, measure the same process conditions as the standard synthesis, the same glass composition, the amount of released gas of synthesis by pure sulfate clarification by the same standard measurement method as a function of temperature, From this, the total amount of released gas related to clarification (SO ₂ + O ₂ ) is determined,
(3)
- to create a curve based on step total quantity of released gas as a function of the sulfate amount used by _{(2) (SO 3) (} SO 2 + O 2),
Plotting the total amount of released gas determined as a function of the amount of sulfate (SO ₃ ) used as a reference in step (1),
By reading the amount of sulfate (SO ₃ ) to be used, which is required in the case of the total amount of outgas (SO ₂ + O ₂ ) similar to the reference,
Determining the amount of sulfate fining agent to be used based on the values determined from step (1) and step (2);
A method for producing transparent glass or transparent pulled glass, which is determined according to the following.   The method according to claim 1, characterized in that the alkaline sulfate or alkaline earth sulfate is selected from sodium sulfate, potassium sulfate, barium sulfate or calcium sulfate. The preferred temperature for the sulfate clarification is as follows:
(1 ') Measure the amount of released gas of the reference synthesis by the standard measurement method in which the clarifier contains antimony and sulfate as a function of temperature, and determine the temperature at which the maximum (SO ₂ + O ₂ ) gas amount is released And
(2 ') Add various sulfate amounts, and measure the same process conditions as the reference synthesis, the same glass composition, and the amount of released gas of the synthesis by pure sulfate clarification by the same standard measurement method as a function of temperature. , (SO ₂ + O ₂ ) determines the temperature at which the amount of gas released becomes maximum,
(3 ') It determines by determining the temperature difference (heating of temperature) of the said sulfate clarification based on the value calculated | required by (1') and (2 '), It is characterized by the above-mentioned. The method described. Creating a gas release curve by plotting the gas release maximum of the gas release measurement according to step (2 ′) as a function of the amount of sulfate used (SO ₃ );
- Read the _{temperature (SO} 2 _{+ O} 2) gas discharge amount for SO ₃ based on the amount sulfate (SO ₃₎ is the maximum value to be used for fining agent, the read temperature is compared with a reference, to introduce 4. Method according to claim 3, characterized in that the temperature difference (temperature warming) of step (3 ') is determined by determining the power temperature difference. Wherein the pulling method, characterized by-option down-draw method or up-draw method or al election process according to any one of claims 1 to 4. Wherein the pulling method, characterized by-option Furukoru method or Asahi type or al election process according to any one of claims 1 to 5. The amount of the sulfate refining agent, characterized in that in the range of 0.2 to 1.5% by weight calculated as SO _3, The method as claimed in any one of claims 6. The method according to any one of claims 1 to 7, wherein the fining temperature is adjusted to a range of 1480 ° C to 1570 ° C. Other fining agents,-chemical bleaching agents, transparently rate change oxidants, iron, characterized in that without the addition of reducing agent The method according to any one of claims 1 to 8.   The melting and clarification are carried out in a melting tank whose energy supply is increased from the front part of the melting tank for melting the batch to the rear part of the melting tank for clarification. The method according to item. Alkaline earth silicate glass with the following component ranges (weight percent on oxide basis):
SiO ₂ 55~75 weight%
Na ₂ O 0-15% by weight
K ₂ O 2~14 weight%
Al ₂ O ₃ 0-15% by weight
MgO 0-4% by weight
CaO (total) 3-12% by weight
BaO 0-15% by weight
ZnO 0-5% by weight
TiO ₂ 0 to 2% by weight
CaO (CaSO ₄ *) 0.5 to 1.5% by weight
* ... The method according to any one of claims 1 to 10, characterized in that it is produced with a fining agent. Alkaline earth silicate glass with the following component ranges (weight percent on oxide basis):
SiO ₂ 65-75% by weight
Na ₂ O 8 to 13 wt%
K ₂ O 4~9 weight%
Al ₂ O ₃ 0 to 2% by weight
MgO 0-4% by weight
CaO (total) 4-9% by weight
BaO 0 to 3 wt%
ZnO 0-5% by weight
TiO ₂ 0 to 2% by weight
CaO (CaSO ₄ *) 0.5 to 1.5% by weight
* ... The method according to any one of claims 1 to 10, characterized in that it is produced with a fining agent. Alkaline earth silicate glass with the following component ranges (weight percent on oxide basis):
SiO ₂ 65-75% by weight
Na ₂ O 8-10% by weight
K ₂ O 6~9 weight%
CaO (total) 4-9% by weight
BaO 1-3 wt%
ZnO 3-5% by weight
TiO ₂ 0 to 2% by weight
CaO (CaSO ₄ *) 0.5 to 1.5% by weight
* ... The method according to any one of claims 1 to 10, characterized in that it is produced with a fining agent.

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